Hypertrophic cardiomyopathy

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Definition

Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle (myocardium) becomes abnormally thick — or hypertrophied. This thickened heart muscle can make it harder for the heart to pump blood. Hypertrophic cardiomyopathy may also affect the heart's electrical system.

Hypertrophic cardiomyopathy often goes undiagnosed, because many of those with hypertrophic cardiomyopathy have few, if any, symptoms. In a small number of people with this condition, the thickened heart muscle can cause signs and symptoms, such as shortness of breath and problems in the heart's electrical system resulting in life-threatening abnormal heart rhythms (arrhythmias).

Fortunately, people with hypertrophic cardiomyopathy often lead normal lives with no significant problems.

Causes

Hypertrophic cardiomyopathy is usually caused by gene mutations. It's thought these mutations cause the heart muscle to grow abnormally thick. People with hypertrophic cardiomyopathy also have an abnormal arrangement of heart muscle fibers. The heart muscle cells become jumbled, known as myofiber disarray. This disarray can contribute to an irregular heartbeat (arrhythmia) in some people.

The severity of hypertrophic cardiomyopathy varies widely. Most people with hypertrophic cardiomyopathy have a form of the disease in which the wall (septum) between the two bottom chambers of the heart (the ventricles) becomes enlarged and obstructs blood flow. This is sometimes referred to as hypertrophic cardiomyopathy with obstruction or hypertrophic obstructive cardiomyopathy.

Sometimes hypertrophic cardiomyopathy occurs without significant obstruction of blood flow. However, the heart's main pumping chamber (the left ventricle) may become stiff, which reduces how much blood the ventricle can hold and how much blood gets pumped out to the body with each contraction. Doctors sometimes refer to this as hypertrophic cardiomyopathy without obstruction or nonobstructive hypertrophic cardiomyopathy.

Risk factors

Hypertrophic cardiomyopathy affects men and women equally.

The condition is usually inherited. There's a 50 percent chance that the children of those with hypertrophic cardiomyopathy will inherit the genetic mutation for the disorder. Siblings of those with hypertrophic cardiomyopathy also are at risk. As a result, close relatives of someone with hypertrophic cardiomyopathy are urged to talk to their doctors about getting screened for the disease.

Complications

In many people, hypertrophic cardiomyopathy doesn't cause significant health problems. However, in some people, hypertrophic cardiomyopathy can cause severe signs and symptoms, such as shortness of breath, chest pain or fainting.

People with hypertrophic cardiomyopathy are at risk of dangerous abnormal heart rhythms (arrhythmias), such as ventricular tachycardia or ventricular fibrillation. These abnormal heart rhythms can cause sudden cardiac death. Hypertrophic cardiomyopathy is the leading cause of heart-related sudden death in people under 30. Fortunately, such deaths are rare.

Possible complications of hypertrophic cardiomyopathy include:

Arrhythmias. Thickened heart muscle, as well as the abnormal structure of heart cells (disarray), can disrupt the normal functioning of the heart's electrical system, resulting in fast or irregular heartbeats. Atrial fibrillation, ventricular tachycardia and ventricular fibrillation are among the arrhythmias that may be caused by hypertrophic cardiomyopathy.

The most dreaded risk of hypertrophic cardiomyopathy is sudden cardiac death due to ventricular tachycardia or ventricular fibrillation. Unfortunately, it can be difficult to predict which people with hypertrophic cardiomyopathy are most prone to these life-threatening, abnormal heart rhythms. If you experience fainting spells, extreme dizziness or prolonged palpitations, you should seek immediate medical care.

Obstructed blood flow. In many people, the thickened heart muscle causes obstruction to blood flow leaving the heart. This can lead to shortness of breath with exertion, chest pain, dizziness and fainting spells.

Mitral valve problems. The thickened heart muscle can leave a smaller space for blood to flow, which in turn causes blood to rush through your heart valves more quickly and more forcefully. This increased force can prevent your mitral valve — the valve between your heart's left atrium and left ventricle — from closing properly. As a result, blood can leak backward into the left atrium. This is called mitral valve regurgitation. Mitral valve regurgitation can lead to other complications, such as heart failure or arrhythmias.

Heart failure. Heart failure means your heart can't pump enough blood to meet your body's needs. The thickened heart muscle of hypertrophic cardiomyopathy can eventually become too stiff to fill effectively, which can lead to shortness of breath and heart failure.

Dilated cardiomyopathy. Over time, thickened heart muscle may become weak and ineffective. The ventricle becomes enlarged (dilated), and its pumping ability becomes less forceful.

Preparing for your appointment

You're likely to start by first seeing your family doctor. However, in some cases when you call to set up an appointment, you may be referred to a doctor who specializes in the diagnosis and treatment of heart conditions (cardiologist).

Here's some information to help you prepare for your appointment.

What you can do

Find out if you need to follow any pre-appointment restrictions, such as changing your activity level or your diet.

Write down any symptoms you're experiencing, and how long you've had them.

Write down key personal information, including any major stresses or recent changes in your life.

Make a list of your key medical information, including other medical problems for which you've recently been treated and the names of any medications you're taking. Your doctor also will want to know if anyone in your family has had hypertrophic cardiomyopathy or has experienced unexplained, sudden death.

Find a family member or friend who can come with you to the appointment, if possible. Someone who accompanies you can help remember what the doctor says.

How soon after I begin treatment can I expect improvement in my symptoms?

If the first treatment isn't effective, what will we try next?

What is my risk of long-term complications?

How will you monitor my health over time?

What restrictions do I need to follow?

Will sexual activity increase my risk of complications?

Do you recommend that I meet with a genetic counselor?

Should my children or other close relatives be screened for this condition?

I have these other health conditions. How can I best manage them together?

Should I see a specialist?

Are there any brochures or other printed material that I can take home with me? What websites do you recommend?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to talk about in-depth. Your doctor may ask:

What are your symptoms?

When did you first begin experiencing symptoms?

Have your symptoms changed over time? If so, how?

Have you ever fainted?

Does exercise or physical exertion make your symptoms worse?

Are you aware of any history of heart problems in your family?

Are you being treated for any other health conditions?

Do you have children or are you planning to have children?

What you can do in the meantime
While you wait for your appointment, check with your family members to find out if any relatives have been diagnosed with hypertrophic cardiomyopathy or have experienced unexplained, sudden death. It will help your doctor to know as many details as possible about your family medical history. If exercise makes your symptoms worse, avoid strenuous exercise until you have seen your doctor and been given specific exercise recommendations.

Tests and diagnosis

A doctor might first suspect hypertrophic cardiomyopathy if he or she hears a heart murmur while listening to the heart. A heart murmur could indicate that the thickened heart muscle is causing abnormal blood flow through the heart.

Echocardiogram is the most common test to diagnose hypertrophic cardiomyopathy. Using echocardiogram images, your doctor can see the thickness of your heart muscle, whether blood flow is obstructed and if your heart valves are moving normally.

An echocardiogram uses sound waves to produce images of the heart. An echocardiogram allows the doctor to see the complicated movement of the heart in motion — ventricles squeezing and relaxing, and valves opening and closing in rhythm with the heartbeat. The doctor can use these images to identify abnormalities in the heart muscle and valves. Types of echocardiograms include:

Transthoracic echocardiogram. This is a standard echocardiogram. A technician (sonographer) spreads gel on your chest and then presses a device known as a transducer firmly against your skin, aiming an ultrasound beam through your chest to your heart. The transducer also detects sound wave echoes reflected by internal structures. A computer converts the echoes into moving images on a monitor. If your lungs or ribs obscure the view, a small amount of intravenous dye may be used to improve the images.

Transesophageal echocardiogram. In this type of echocardiogram, a flexible tube containing a transducer is guided down your throat and into your esophagus, which connects your mouth to your stomach. From there, the transducer can get more-detailed images of your heart. Your doctor might order a transesophageal echocardiogram if it's difficult to get a clear picture of your heart with a standard echocardiogram or if he or she wants to further examine your mitral valve.

Additional tests might be done to help look for other effects of hypertrophic cardiomyopathy and help determine what sort of treatment could be needed. These additional tests include:

Electrocardiogram (ECG). This test records the electrical activity of your heart. It's done to detect abnormal electrical signals that may result from the thickened heart muscle.

Holter monitor. This is a portable ECG that records a continuous electrocardiogram of your heart, usually over the course of one to two days. It's used to detect abnormal heart rhythms.

Cardiac catheterization. Sometimes your doctor may use this test to measure the pressure of blood flow inside your heart. A catheter is inserted into an artery, starting in your groin area. It's then carefully threaded to your heart chambers under guidance of an X-ray machine that shows real-time images of your body. Dye is injected through the catheter, and the X-ray machine makes images (angiograms) of your heart and blood vessels.

Cardiac MRI. Cardiac magnetic resonance imaging (MRI) is an imaging technique that uses magnetic fields and radio waves to create images of your heart. Cardiac MRI is often used in addition to echocardiography, particularly if the echocardiographic images are not conclusive.

Testing approaches for first-degree relatives
Genetic tests are available that may be able to help your doctor diagnose hypertrophic cardiomyopathy. However, the genetic causes of hypertrophic cardiomyopathy aren't fully understood. More than 10 genes have been identified so far that can make you more susceptible to hypertrophic cardiomyopathy.

Because of the complex nature of how your genes interact, genetic tests often don't give a definitive answer. In addition, insurance companies may not cover the testing. Talk with your doctor about whether genetic testing could be an option for you.

If you have a first-degree relative — parent, sibling or child — with hypertrophic cardiomyopathy, experts recommend that you be screened regularly for signs of this condition starting at puberty (about age 12) or when you begin competitive athletics. The recommendation is to have an echocardiogram and electrocardiogram once each year until you reach adulthood (about age 18) and stop competitive athletics. If no evidence of hypertrophic cardiomyopathy is found by the time you reach adulthood, your doctor may recommend adjusting your screening schedule to once every five years.

Treatments and drugs

The goals of treatment for hypertrophic cardiomyopathy are to relieve symptoms and prevent sudden cardiac death in those at high risk.

Treatment options for hypertrophic cardiomyopathy include drugs, surgery or other methods to destroy obstructive heart tissue or implantation of devices to help control heart rhythm.

Drug treatment. Various medications can help relax the muscle and slow the rate so that the heart can pump more efficiently. Some of the drugs your doctor may suggest include beta blockers, calcium channel blockers or the anti-arrhythmic medications disopyramide or amiodarone.

Septal myectomy. This is an open-heart operation in which the surgeon removes part of the thickened, overgrown heart muscle wall (septum) that separates the two bottom heart chambers (ventricles). Removing part of this overgrown muscle improves blood flow and reduces mitral regurgitation. Myectomy is used if medications don't relieve symptoms. Most people who have symptoms and undergo myectomy have no further symptoms. This type of surgery is available only in medical centers that specialize in the treatment of hypertrophic cardiomyopathy.

Septal ablation. Also called septal alcohol ablation, this is a treatment in which a small portion of the thickened heart muscle is destroyed by injecting alcohol through a catheter into the artery supplying blood to it. There are possible complications with this procedure, including heart block — a disruption of the heart's electrical system — which requires implantation of a pacemaker.

Pacemaker implantation. A pacemaker is a small electronic device inserted under your skin that sends electrical signals to your heart to monitor and regulate your heartbeat. Surgery to implant the pacemaker is usually performed under local anesthesia and typically takes less than three hours. Pacemaker implantation is generally not as effective as surgical options, but it's sometimes used in older people who want to avoid more invasive procedures.

Implantable cardioverter-defibrillator (ICD). This is a pager-sized device implanted in your chest like a pacemaker. An ICD continuously monitors your heartbeat. If a life-threatening arrhythmia occurs, the ICD delivers precisely calibrated electrical shocks to restore a normal heart rhythm. Some people with hypertrophic cardiomyopathy are at risk of sudden cardiac death because of abnormal heart rhythms. In these high-risk individuals, many doctors recommend the implantation of an ICD.

People with hypertrophic cardiomyopathy who may be candidates for ICD implantation include those with:

Prior cardiac arrest

One or more family members with sudden death caused by hypertrophic cardiomyopathy

Unexplained fainting

Episodes of rapid heartbeat

Blood pressure that fails to rise during exercise testing

An echocardiogram that detects extreme thickness of the left ventricular wall

Lifestyle and home remedies

Your doctor will recommend a number of key lifestyle restrictions to reduce your risk of hypertrophic cardiomyopathy-related complications. You'll likely need to follow restrictions for your:

Physical activity level. Competitive sports are generally not safe for people with hypertrophic cardiomyopathy. In some cases, you may be able to participate in low-intensity physical activities. Ask your doctor for guidance.

Diet. A healthy diet is an important part of maintaining your heart health. In some cases, you may need to follow a special diet.

Alcohol use. Drinking too much alcohol can trigger irregular heart rhythms, such as atrial fibrillation. If you drink alcohol, ask your doctor for specific guidance about what levels of alcohol are safe.

Coping and support

Being diagnosed with hypertrophic cardiomyopathy can cause a range of difficult emotions and fears. Like many people with this condition, you're likely to struggle with feelings of grief, fear and anger. These are appropriate responses to the serious changes that come with your diagnosis, including exercise restrictions, a lifelong reliance on medications, fear of death and fear of passing the condition on to your children.

Talk with your doctor if you are feeling hopeless, panicked or unable to cope. It may help to talk with a therapist. In some cases, your doctor also may recommend medications that treat mental health problems such as anxiety and depression.

In other cases, your mental health may benefit most from talking with medical experts, such as your medical care team or a genetic counselor, who can help you understand your risks and find effective ways of coping.

Prevention

Because hypertrophic cardiomyopathy is inherited, it can't be prevented. However, doctors and scientists are learning more about the genetic mutations that cause the disorder. Though the condition itself can't be prevented, it's important to identify this condition as early as possible to guide treatment and prevent complications.

Preventing sudden death
The use of an implantable cardioverter-defibrillator has been shown to help prevent sudden cardiac death, which occurs rarely in those with hypertrophic cardiomyopathy.

Unfortunately, because many people with hypertrophic cardiomyopathy don't realize they have it, there are instances where the first sign of a problem is sudden cardiac death. These cases can happen in seemingly healthy young people, including high school athletes and other young, active adults. News of these types of deaths generates understandable attention because they're so unexpected, but parents should be aware these deaths are quite rare.

Still, experts in heart abnormalities generally recommend that those with hypertrophic cardiomyopathy not participate in most competitive sports, with the possible exception of some low-intensity sports. You should talk with your cardiologist about specific recommendations. The use of an implantable cardioverter-defibrillator should not be viewed as a substitute for these recommendations.